> This still requires the platform to detect _genuine_ transgressions which is very difficult.

I had in mind situations where a seller contacts a buyer who has left a negative review, and offers free merchandise for changing the review. If it happens within Amazon's system, they should be able to verify it.

Obviously an attack you have to defend against is unscrupulous seller E posting fake review requests on Facebook (or wherever) "on behalf of" honest seller A, causing Amazon to ban / punish A in the rankings.